It is well known in the spinning of polyurethane elastic filaments that a liquid finishing agent such as an oil is applied to the filaments for prevention of their damage which may be caused by their abrasion, and conferring smoothness thereon to facilitate their handling in the subsequent steps.
A conventional means for application of a finishing agent takes a roller system in which a roller partially immersed in a bath containing the finishing agent is rotated to form a uniform layer of the finishing agent on the roller surface and a polyurethane elastic filament is allowed to run while being brought into contact with this surface to apply the finishing agent thereto.
Another example is a guide system, so called in general, in which a finishing agent such as an oil is supplied to a slit or groove provided in the guide and a polyurethane filament is allowed to run through the slit or groove to apply the finishing agent thereto.
It is also well known that spun filaments of a polyurethane material are subjected to false twisting upstream in their running direction from the finishing agent applying means. FIG. 1 shows the schematic diagram of a conventional apparatus for spinning of polyurethane elastic filaments. In this apparatus, a melt or solution of a polyurethane material is supplied from the conduit 12 and extruded through the spinning nozzle 14 into the spinning tube 15. At that time, warm air or cold air is always introduced from the inlet 13 into the spinning tube 15 and exhausted through the outlet 16. The air flow facilitates the formation of a filament 4 from the extruded melt or solution. The filament 4 coming out through a slit at the bottom of the spinning tube 15 is subjected to false twisting by the false twisting means 17, and a finishing agent is applied to the false twist filament by the finishing agent applying means 18, after which the false twist filament is wound up on the first roller 19 or allowed to turn its running direction to a certain direction for final winding.
In a conventional means for application of a finishing agent, whichever it takes either the roller system or the guide system as described above, a polyurethane elastic filament, although it is finally wound up with a winding machine after the application, is inevitably brought into contact with the application face of this means before or simultaneously with the application. The filament before its contact with the application face is in an extremely unstable state (i.e., not yet completely solidified), which is aggravated by a variation in the frictional resistance on this face, so that the properties of the wound filament, particularly its evenness, may be adversely affected.
Further, in the conventional spinning apparatus, when a polyurethane elastic filament is subjected to false twisting with a revolving gas flow or by mechanical rotation, it is brought into contact with a certain solid face of the false twisting means at the time of false twisting. A variation in the running frictional resistance of the filament is caused by the false twisting or its contact with the solid face. This variation has an adverse effect on the filament in an unstable state, i.e., not yet completely solidified, just after the extrusion through the spinning nozzle, to cause a phenomenon such as waviness and cramp in the filament, which may adversely affect on the evenness of the filament and may finally give rise to even filament breaking.